Schrödinger’s Cat

In 1935, Erwin Schrödinger, in an attempt to explain the Copenhagen interpretation of quantum physics, proposed an experiment where a cat is placed in a box with a sealed vial of poison that will break open at a random time.

Since no-one knows when or if the poison has been released, until the box is opened, the cat can be thought of as both alive and dead.

It is only by opening the box that you will find out which it is.

— Adapted from ‘The Big Bang Theory’.